1. Field of the Invention
The present invention relates to a wire clamper used in a wire bonding apparatus.
2. Prior Art
Japanese Patent Application Publication (Kokoku) No. 61-2294 discloses one of the conventional wire clampers.
This wire clamper includes a movable arm and a fixed arm. The movable arm is urged toward the fixed arm by a spring, and the movable arm is opened and closed by a solenoid. When the solenoid is energized, the movable arm is pushed by the projecting rod of the solenoid, overcoming the driving force of the spring. The movable ar is thus opened. When the power to the solenoid is cut off, the movable arm is closed by the spring, thus holding the wire between the movable arm and the fixed arm.
Since this prior art clamper uses a solenoid to open and close the arm parts of the clamper, there are several problems. The overall weight of the clamper tends to be heavy, and the clamping action or the response of the clamper is slow. In addition, since the load which retains the wire (i. e., the clamping load) is obtained by the driving force of the spring, which is approximately 40 to 50 g, the movable arm tends to be unsteady when the bonding head moves at high speed. This means that the clamping load is unstable. Moreover, since the clamping load is obtained by the spring, the spring must be replaced when the amount of clamping load needs to be changed. In addition, a desired clamping load is usually not obtained easily, and the adjustment of the clamping load requires a considerable amount of time.